The present invention relates to baghouse filters for cleaning a gas by separating from the gas solid particles entrained therein and, more specifically, to a baghouse filter incorporating a collapsible filter bag assembly which is readily removable out of the baghouse to permit inspection, repair, and replacement of the bag filter assembly or the filter bags associated therewith to take place externally of the baghouse.
A typical baghouse filter is constructed of a plurality of filter bags suspended in an enclosure termed a baghouse. Each filter bag is a cylindrically elongated porous fabric member having an open end which is attached to a tube sheet. The filter bags and the tube sheet divide the baghouse into two chambers, one chamber comprising the space external to the bags and the other comprising the space internal to the bags.
In operation a dirty gas, i.e., a gas laden with entrained solid particles, is drawn through the baghouse. Entering through one chamber as dirty gas, the gas passes through the fabric filters to leave through the other chamber as a clean gas. As the gas flows through the fabric, the entrained solid particles being too large to pass through the pores of the fabric, collect on the surface of the fabric and are thereby filtered from the gas. In many cases, the filter bags are exposed to a very hostile environment. It is not uncommon for the gas being cleaned to have a temperature of 150.degree. C. or more and contain corrosive compounds such as acid mist. Consequently, the fabric of the filter bags is subject to tearing and erosion resulting in a hole in the bag through which dirty gas can pass into the clean gas and thereby reduce dust collection efficiency. In order to avoid this most undesirable occurrence, it is customary to frequently visually inspect the filter bags for tears or holes in the fabric. If this examination takes place inside the baghouse, the inspection personnel are exposed to a hot, dust laden, poorly-ventilated environment and generally must perform the work in very cramped space. Typically, inspection personnel must walk along a catwalk-like structure disposed permanently within the baghouse in order to reach each of the numerous filter bags.
The desirability of being able to inspect and replace filter bags at a location external to the baghouse has been long recognized. One bag filter system which allows external access to the filter bags is disclosed in U.S. Pat. No. 3,486,310. Shown therein is a bag filter unit comprising a plurality of bags mounted to a rotating tube sheet. In order to replace the filter bags, the tube sheet is progressively rotated so that each filter bag in turn appears before an access opening thereby enabling personnel located outside of the baghouse enclosure to reach each bag. Unfortunately, such an arrangement precludes arranging the bags in a compact design. As baghouses, even when compactly designed, generally require more space than other dust collection equipment, such a limitation is a serious drawback.
Another prior art scheme designed to permit external inspection of the filter bags is the removable bag filter unit disclosed in U.S. Pat. No. 3,788,046. As disclosed therein, the entire bag filter unit is mounted on wheels so that it may be removed from the baghouse enclosure for inspection. Since filter bags may typically range in length from three meters to upwards of eight meters, a bag filter unit is of necessity quite tall. Thus, a very large access opening, which must be sealed against gas leakage, must be provided in the wall of the baghouse enclosure in order to remove the bag filter unit. Further, sufficient space must be allotted outside of the enclosure to allow removal of the bag filter unit and permit placement of access platforms about the removed unit.
Therefore, there is evidenced the need for a baghouse design which permits external inspection of the filter bag assembly while at the same time allowing for a compact, space-saving design. Accordingly, it is an object of the present invention to provide a unique bag filter assembly which, while being readily removable from the baghouse enclosure, minimizes the space requirements necessary for such removal and for the subsequent inspection process to take place.